Bubbles on the wrist if pressure put on the palm. No pain. What are these?

Yes on my wrist , if I put pressure on my palm. Little air bubbles of skin inflate on my wrist. They are soft and seem hollow. I have some on my feet I find every now and then when sitting in a weird position. These bubbles don t hurt but I would like to know what they are :) I could ask my doctor the next time I see one but I figured I could find the answer here . My freinds have them too. It seems normal . What causes them? What are they ? All I want to know